code: def test_none(self):
      x = (numpy.zeros((1, 2, 3), dtype=numpy.float64),)
      y = G().apply(x)
      assert y[0].data is None
  
file_path: chainer/tests/chainer_tests/utils_tests/test_precision.py
imports: import unittest
  import numpy
  from chainer import function_node
  from chainer import testing
  from chainer.utils import precision
label_desc: Use image node_id 5 for calling the TestMixedPrecision obj's underlying member method code with example usage: obj.test_none() without return types